Green sheet coating material, green sheet, production method of green sheet and production method of electronic device

ABSTRACT

A green sheet coating material includes ceramic powder and a binder resin containing a butyral based resin as the main component, which furthermore includes a xylene based resin as a tackifier. The xylene based resin is included in a range of 1.0 wt % or less, more preferably 0.1 or more and 1.0 wt % or less, and particularly preferably more than 0.1 and 1.0 wt % or less with respect to 100 parts by weight of ceramic powder.

TECHNICAL FIELD

The present invention relates to a green sheet coating material, a greensheet, a production method of a green sheet coating material aproduction method of a green sheet, and a production method of anelectronic device and, particularly relates to a coating material, greensheet and a method capable of producing a green sheet having excellenthandlability and adhesiveness even in the case of an extremely thinsheet and suitable to making an electronic device a thin layer andmultilayer.

BACKGROUND ART

In recent years, as a variety of electronic equipments become compact,electronic devices to be installed inside the electronic equipments havebecome more compact and higher in performance. As one of the electronicdevices, there is a ceramic electronic device, such as a CR built-insubstrate and a multilayer ceramic capacitor, and the ceramic electronicdevices have been required to be more compact and higher in performance.

To pursue a more compact ceramic electronic device having a highercapacity, there is a strong demand for making a dielectric layerthinner. Recently, a thickness of a dielectric green sheet composing adielectric layer has become a several μm or less.

To produce a ceramic green sheet, normally, a ceramic coating materialcomposed of ceramic powder, a binder (an acrylic based resin and abutyral based resin, etc.), a plasticizer (phthalate esters, glycols,adipic acids, and phosphoric esters) and an organic solvent (toluene,MEK and acetone, etc.). Next, the ceramic coating material coated on acarrier sheet (a supporting body made by PET and PP) by using the doctorblade method, etc. and dried by heating.

Also, a method of producing by preparing a ceramic suspension whereinthe ceramic powder and binder are mixed in a solvent, then, biaxialstretching a film-shaped molded item obtained by molding the suspensionhas been considered in recent years.

A method of producing a multilayer ceramic capacitor by using theceramic green sheet explained above will be explained in detail. Aninternal electrode conductive paste containing metal powder and a binderis printed to be a predetermined pattern on the ceramic green sheet anddried to form an internal electrode pattern. After that, the green sheetis peeled from the carrier sheet and stacked by a predetermined numberof layers. Here, two methods are proposed, that are a method of peelingthe green sheet from the carrier sheet before stacking in layers and amethod of peeling the carrier sheet after stacking in layers andadhering by compression, but the difference is not large. Finally, thestacked body is cut to be chips, so that green chips are prepared. Afterfiring the green chips, external electrodes are formed, so that amultilayer ceramic capacitor and other electronic devices are produced.

When producing a multilayer ceramic capacitor, an interlayer thicknessof sheets formed with internal electrodes is in a range of 3 μm to 100μm or so based on a desired capacitance required as a capacitor. Also,in a multilayer ceramic capacitor, a part not formed with internalelectrodes is formed on an outer part in the stacking direction of thecapacitor chip.

In such a multilayer ceramic capacitor, a polyvinyl butyral resin havinga polymerization degree of 1000 or less (Mw=50,000) is used as a binderin some cases (refer to the Japanese Patent Publication No. 10-67567).However, in the case of using a normal polyvinyl butyral resin as abinder, there are problems that adhesiveness declines and stackingbecomes difficult when a thickness of the green sheet becomes thin.

In recent years, as electronic equipments become more compact,electronic devices to be used therein have rapidly become more compact.In multilayer electronic devices as typified by a multilayer ceramiccapacitor, rapid development has been made on increasing the number oflayers to be stacked and attaining a thinner interlayer thickness. Torespond to the technical trends, a thickness of a green sheet, whichdetermines the interlayer thickness, has almost become 3 μm or less to 2μm or less. Therefore, in a production process of a multilayer ceramiccapacitor, it is necessary to handle extremely thin green sheets and todesign very advanced green sheet properties.

As characteristics required as the properties of such an extremely thingreen sheet, sheet strength, flexibility, smoothness, adhesiveness whenbeing stacked, handlability (electrostatic property), etc. may bementioned, and balance of a higher order is required.

Note that, as shown in the Japanese Unexamined Patent Publication No.6-206756, there is known a technique of using a polyvinyl butyral resinhaving a polymerization degree of 1000 or more as a binder in greensheet slurry containing an aqueous solvent for a purpose of eliminatinga short-circuiting defect.

However, the Japanese Unexamined Patent Publication No. 6-206756 is notfor particularly attaining a thinner organic solvent based green sheet,and it also has problems that the adhesiveness declines and stackingbecomes difficult when a thickness of the green sheet is made thin.

Also, as a method of improving adhesiveness of the green sheet, as shownin the Japanese Unexamined Patent Publication No. 5-279108, there isknown a method of making a hot-melt adhesive, such as rosin, containedin dielectric slurry. However, in this method, adhesiveness at a hightemperature can be expected but it does not lead to an improvement ofadhesive strength at a normal temperature and, when the dielectric layeris made thin, adhesive strength at a normal temperature is insufficientand stacking is not easy.

Furthermore, as disclosed in the Japanese Unexamined Patent PublicationNo. 7-99132, a method of using a water-soluble polyvinyl acetal resin asa binder resin and adding amines as a plasticizer is proposed. However,in this method, the binder resin and the plasticizer are selected onlyconsidering the adhesiveness, and other sheet properties, such astensile strength and surface roughness, may decline when the dielectriclayer is made thin.

Furthermore, as disclosed in the Japanese Unexamined Patent PublicationNo. 10-166343, there is provided a method of applying to a surface ofthe green sheet a self-adhesion inductive liquid for dissolving orswelling a binder resin in a green sheet. However, in this method, astep of applying the liquid on the surface of the produced green sheetis furthermore added, so that the procedure becomes cumbersome andcomplicated.

Also, as disclosed in the Japanese Unexamined Patent Publication No.13-106580, a method of using a polyvinyl acetal resin as a binder resinand adding phthalate ester based, glycol based and amino alcohol basedplasticizers as a plasticizer is proposed. However, in this method, aplurality of kinds of plasticizers are used and other sheet properties,such as tensile strength and surface roughness, decline when thedielectric layer is made thin.

Furthermore, as disclosed in the Japanese Unexamined Patent PublicationNo. 14-104878, a method of mixing a plurality of kinds of polyvinylacetal resins as a binder is proposed. However, in this method, mixingof resin kinds is performed by only considering an improvement of theadhesiveness, and other sheet properties, such as tensile strength andsurface roughness, decline when the dielectric layer is made thin.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a green sheet coatingmaterial, a green sheet, a production method of a green sheet coatingmaterial and a production method of a green sheet capable of producing agreen sheet having enough strength to be peeled from a supporting body,preferable adhesiveness and handlability even if the green sheet isextremely thin. Also, another object of the present invention is toprovide a production method of an electronic device suitable to be madethin and multilayer.

The present inventors have been committed themselves to study to attainthe above objects, found that it was possible to produce a green sheethaving enough strength to be peeled from a supporting body, preferableadhesiveness and handlability even if the green sheet was extremelythin, by using as a binder a polyvinyl acetal resin or other butyralbased resin and using a xylene based resin as a tackifier, and completedthe present invention.

Namely, a green sheet coating material according to the presentinvention comprises ceramic powder and a binder resin containing abutyral based resin as the main component; and

furthermore comprising a xylene based resin as a tackifier.

A xylene resin is not particularly limited and an addition condensationresin of methaxylene and formalin, and those obtained by modifying theaddition condensation resin by a variety of phenols and alcohol may bementioned. A preferable average molecular weight of a xylene based resinin the present invention is 200 to 600 in those not modified. Thosemodified are not limited to this.

By combining a binder resin including a butyral based resin as the maincomponent and an adhesive agent made by a xylene based resin, it becomespossible to produce a green sheet having enough strength to be peeledfrom a supporting body, preferable adhesiveness and handlability evenwhen the green sheet is extremely thin. For example, it becomes possibleto make a thickness of the dielectric layer after firing (a green sheetafter firing) to 5 μm or less, preferably 3 μm or less, and morepreferably 2 μm or less. Also, the number of layers to be stacked can beincreased.

Preferably, said xylene based resin is contained in a range of 1.0 wt %or less, more preferably 0.1 or more and 1.0 wt % or less, andparticularly preferably more than 0.1 and 1.0 wt % or less with respectto 100 parts by weight of said ceramic powder. When a content of thexylene resin is too small, the adhesiveness tends to decline. While whenthe content is too much, although the adhesiveness improves, it isliable that the sheet surface roughness becomes rougher, stacking of thelayers by a large number becomes difficult, tensile strength of thesheet declines, and handlability of the sheet declines.

Preferably, said butyral based resin is a polybutyral resin; and

a polymerization degree of said polybutyral resin is 1000 or higher and1700 or lower, a butyralation degree of the resin is higher than 64% andlower than 78%, and a residual acetyl group amount is less than 6%.

When a polymerization degree of the polybutyral resin is too small, itis liable that sufficient mechanical strength is hard to be obtainedwhen the layer is made as thin as, for example, 5 μm or less, andpreferably 3 μm or less. While, when the polymerization degree is toolarge, the surface roughness tends to deteriorate when made to be asheet. Also, when a butyralation degree of the polybutyral resin is toolow, solubility to the coating material tends to decline, while when toohigh, sheet surface roughness tends to decline. Furthermore, when aresidual acetyl group amount is too much, the sheet surface roughnesstends to increase.

Preferably, wherein said binder resin is contained by 5 parts by weightor more and 6.5 parts by weight or less with respect to 100 parts byweight of said ceramic powder. When a content of the binder resin is toosmall, it is liable that the sheet strength declines and stackability(adhesiveness at the time of stacking) deteriorates. Also, when thecontent of the binder resin is too much, it is liable that segregationof the binder resin is caused to deteriorate the dispersibility, andsheet surface roughness deteriorates.

Preferably, dioctyl phthalate is contained as the plasticizer by 40parts by weight or more and 70 parts by weight or less with respect to100 parts by weight of the binder resin. Comparing with otherplasticizers, dioctyl phthalate is preferable in terms of both of sheetstrength and sheet ductility, and particularly preferable because therelease strength from a supporting body is small and it is easilypeeled. Note that when a content of the plasticizer is too small, it isliable that sheet stretching becomes less and flexibility becomes less.Also, when the content is too large, it is liable that bleeding of theplasticizer from the sheet is caused, segregation of the plasticizer iseasily caused against the sheet, and the sheet dispersibility declines.

A production method of a ceramic green sheet according to the presentinvention includes:

a step of preparing the above green sheet coating material; and

a step of forming a ceramic green sheet by using the green sheet coatingmaterial.

A production method of a ceramic electronic device according to thepresent invention includes:

a step of preparing the above green sheet coating material;

a step of forming a ceramic green sheet by using the green sheet coatingmaterial;

a step of drying the green sheet;

a step of stacking dried green sheets via internal electrode layers toobtain a green chip; and

a step of firing the green chip.

The green sheet according to the present invention is produced by usingthe above green sheet coating material.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of a multilayer ceramic capacitoraccording to an embodiment of the present invention; and

FIG. 2 is a sectional view of a key part showing a production procedureof the multilayer ceramic capacitor shown in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Below, the present invention will be explained based on the embodimentshown in the drawings.

First, as an embodiment of an electronic device produced by using agreen sheet coating material (dielectric paste) and a green sheetaccording to the present invention, an overall configuration of amultilayer ceramic capacitor will be explained.

As shown in FIG. 1, a multilayer ceramic capacitor 2 according to thepresent embodiment comprises a capacitor element 4, a first terminalelectrode 6 and a second terminal electrode 8. The capacitor element 4comprises dielectric layers 10 and internal electrode layers 12, and theinternal electrode layers 12 are stacked alternately between thedielectric layers 10. The alternately stacked internal electrode layers12 on one side are electrically connected to inside of the firstterminal electrode 6 formed at one end portion of the capacitor element4. Also, the alternately stacked internal electrode layers 12 on theother side are electrically connected to inside of the second terminalelectrode 8 formed at the other end portion of the capacitor element 4.

A material of the dielectric layer 10 is not particularly limited andcomposed of a dielectric material, for example, calcium titanate,strontium titanate and/or barium titanate, etc. A thickness of each ofthe dielectric layers 10 is not particularly limited, but those having athickness of several μm to several hundreds of μm are general.Particularly in the present embodiment, it is made to be thin aspreferably 5 μm or less, and more preferably 3 μm or less.

A material of the terminal electrodes 6 and 8 is not particularlylimited, either, and copper, a copper alloy, nickel and a nickel alloy,etc. are normally used. A silver and an alloy of silver with palladiummay be also used. A thickness of the terminal electrodes 6 and 8 is notparticularly limited, either, but is normally 10 to 50 μm or so.

A shape and size of the multilayer ceramic capacitor 2 may be suitablydetermined in accordance with the object and use. When the multilayerceramic capacitor 2 has a rectangular parallelepiped shape, it isnormally a length (0.6 to 5.6 mm, preferably 0.6 to 3.2 mm)×width (0.3to 5.0 mm, preferably 0.3 to 1.6 mm)×thickness (0.1 to 1.9 mm,preferably 0.3 to 1.6 mm) or so.

Next, an example of production methods of the multilayer ceramiccapacitor 2 according to the present embodiment will be explained.

(1) First, a dielectric coating material (green sheet coating material)is prepared to produce a ceramic green sheet for composing thedielectric layers 10 shown in FIG. 1 after firing.

The dielectric coating material is composed of an organic solvent basedcoating material obtained by kneading a dielectric material (ceramicpowder) and an organic vehicle.

The dielectric material is suitably selected from a variety of compoundswhich become composite oxides or oxides, such as carbonates, nitrites,hydroxides, and organic metal compounds, and mixed for use. Thedielectric material is normally used as powder having an averageparticle diameter of 0.1 to 0.3 μm or less, and preferably 0.4 μm orless or so. Note that it is preferable to use finer powder than thegreen sheet thickness to form an extremely thin green sheet.

The organic vehicle is obtained by dissolving a binder resin in anorganic solvent. As the binder resin used for the organic vehicle, apolyvinyl butyral resin is used in the present embodiment. Apolymerization degree of the polybutyral resin is 1000 or higher and1700 or lower, and preferably 1400 to 1700. Also, a butyralation degreeof the resin is higher than 64% and smaller than 78%, and preferablyhigher than 64% and 70% or lower, and the residual acetyl group amountis less than 6% and preferably 3% or less.

The polymerization degree of the polybutyral resin can be measured, forexample, by a polymerization degree of a polyvinyl acetal resin as amaterial. Also, the butyralation degree can be measured, for example,based on the JISK6728. Furthermore, the residual acetyl group amount canbe measured based on the JISK6728.

When the polymerization degree of the polybutyral resin is too low, itis liable that sufficient mechanical strength is hard to be obtainedwhen made to be a thin film of, for example, 5 μm or less, andpreferably 3 μm or less or so. Also, when the polymerization degree istoo large, surface roughness tends to increace when made to be a sheet.Also, when the butyralation degree of the polybutyral resin is too low,solubility in a coating material tends to decline, while when too high,sheet surface roughness tends to increase. Furthermore, when theresidual acetyl group amount is too large, sheet surface roughness tendsto increace.

An organic solvent to be used for an organic vehicle is not particularlylimited and an organic solvent, such as terpionel, alcohol, butylcarbitol, acetone and toluene, is used. In the present embodiment, theorganic solvent preferably contains an alcohol based solvent and anaromatic solvent, and the aromatic solvent is contained by 10 parts byweight or more and 20 parts by weight or less when assuming total weightof the alcohol based solvent and aromatic solvent is 100 parts byweight. When a content of the aromatic solvent is too small, sheetsurface roughness tends to increase, while when too large, the coatingmaterial filtration properties decline and sheet surface roughness alsoincrease.

As an alcohol based solvent, methanol, ethanol, propanol and butanol,etc. may be mentioned. As an aromatic solvent, toluene, xylene andbenzyl acetate, etc. may be mentioned.

It is preferable that a binder resin is dissolved in an alcohol basedsolvent of at least one kind of methanol, ethanol, propanol and butanoland filtered to be a solution in advance, and dielectric powder andother components are added to the solution. A binder resin having a highpolymerization degree is hard to be dissolved in a solvent, anddispersibility of a coating material tends to decline in a normalmethod. In a method of the present embodiment, a binder resin having ahigh polymerization degree is dissolved in the above good solvent andceramic powder and other components are added to the solution, so thatdispersibility of a coating material can be improved and generation ofundissolved resin can be suppressed. Note that solid contentconcentration cannot be raised and changes of lacquer viscosity tend tobecome large over time in the case of a solvent other than the abovesolvents.

In the present embodiment, the dielectric coating material is added witha xylene based resin as a tackifier together with the binder resin. Thexylene based resin is added in a range of 1.0 wt % or less, morepreferably 0.1 or more and 1.0 wt % or less, and particularly preferablymore than 0.1 and 1.0 wt % or less with respect to 100 parts by weightof ceramic powder. When the adding quantity of the xylene based resin istoo small, the adhesiveness tends to decline. When the adding quantityis too much, although the adhesiveness improves, it is liable that sheetsurface roughness becomes rougher, stacking of layers by a large numberbecomes difficult, tensile strength of the sheet declines andhandlability of the sheet declines.

In the dielectric coating material, additives selected from a variety ofdispersants, plasticizers, antistatic agents, dielectrics, glass flit,and insulators may be included in accordance with need.

In the present embodiment, a dispersant is not particularly limited, butpolyethylene glycol based nonionic dispersant is preferably used, and ahydrophile-lipophile balance (HLB) value thereof is 5 to 6. A dispersantis added by 0.5 part by weight or more and 1.5 parts by weight or less,and more preferably 0.5 part by weight or more and 1.0 part by weight orless with respect to 100 parts by weight of ceramic powder.

When the HLB is out of the above ranges, it is liable that coatingmaterial viscosity increases and sheet surface roughness increases.Also, in the case of a dispersant other than a polyethylene glycol basednonionic dispersant, coating material viscosity increases, sheet surfaceroughness increases and sheet ductility declines, so that it is notpreferable.

When an adding quantity of a dispersant is too small, sheet surfaceroughness tends to increase, while when too large, sheet tensilestrength and stackability tend to decline.

In the present embodiment, dioctyl phthalate is preferably used as aplasticizer and contained by an amount of preferably 40 parts by weightor more and 70 parts by weight or less, and more preferably 40 to 60parts by weight with respect to 100 parts by weight of a binder resin.Comparing with other plasticizers, dioctyl phthalate is preferable interms of both of sheet strength and sheet stretch and is particularlypreferable for having weak peeling strength so as to be easily peeledfrom a supporting body. Note that when a content of the plasticizer istoo small, it is liable that sheet stretch becomes less and flexibilitybecomes less. Also, when the content is too large, it is liable thatbleeding of a plasticizer from a sheet is caused, segregation of theplasticizer against the sheet easily arises and dispersibility of thesheet declines.

Also, in the present embodiment, the dielectric coating materialcontains water by 1 part by weight or more and 6 parts by weight orless, and preferably 1 to 3 parts by weight with respect to 100 parts byweight of dielectric powder. When a water content is too small, changesof coating material characteristics due to moisture absorbance over timebecomes large, coating material viscosity tends to increase andfiltration properties of the coating material tend to decline. Whilewhen the water content is too large, separation and precipitation of thecoating material are caused, the dispersibility becomes poor and surfaceroughness of the sheet tends to decline.

Furthermore, in the present embodiment, at least any one of ahydrocarbon based solvent, industrial gasoline, kerosene, and solventnaphtha is added by preferably 3 parts by weight or more and 15 parts byweight or less, and more preferably 5 to 10 parts by weight with respectto 100 parts by weight of dielectric powder. By adding these additives,sheet strength and sheet surface roughness can be improved. When anadding quantity of these additives is too small, effects of adding issmall, while when the adding quantity is too large, it is liable thatsheet strength and sheet surface roughness are deteriorated inversely.

A binder resin is contained preferably by 5 parts by weight or more and6.5 parts by weight or less with respect to 100 parts by weight ofdielectric powder. When a content of the binder resin is too small, itis liable that the sheet strength declines and stackability(adhesiveness at the time of stacking in layers) also declines. Whilewhen a content of the binder resin is too large, it is liable thatsegregation of the binder resin is caused to make the dispersibilityworse and sheet surface roughness tends to increase.

When assuming that total volume of the ceramic powder, binder resin andplasticizer is 100 volume %, a volume ratio accounted by the dielectricpowder is preferably 62.42% or more and 72.69% or less, and morepreferably 63.93% or more and 72.69% or less. When the volume ratio istoo small, it is liable that segregation of the binder is easily causedto make the dispersibility worse and surface roughness declines. Also,when the volume ratio is too large, it is liable that the sheet strengthdeclines and the stackability also declines.

Furthermore, in the present embodiment, the dielectric coating materialpreferably includes an antistatic agent, and the antistatic agent ispreferably imidazoline based antistatic agent. When the antistatic agentis not an imidazoline based antistatic agent, the antistatic effect issmall and the sheet strength, sheet ductility or adhesiveness tends todecline.

An antistatic agent is contained by 0.1 part by weight or more and 0.75part by weight or less, and more preferably 0.25 to 0.5 part by weightwith respect to 100 parts by weight of ceramic powder. When an addingquantity of the antistatic agent is too small, the antistatic effectbecomes small, while when too large, it is liable that surface roughnessof the sheet increase and sheet strength declines. When the antistaticeffect is too small, electrostatic easily arises when peeling thecarrier sheet as a supporting body from the ceramic green sheet, and adisadvantage that the green sheet gets wrinkled, etc. easily arises.

By using the dielectric coating material, as shown in FIG. 2, a greensheet 10 a is formed to be a thickness of preferably 0.5 to 30 μm, andmore preferably 0.5 to 10 μm or so on the carrier sheet 30 as asupporting sheet by the doctor blade method, etc. The green sheet 10 ais dried after being formed on the carrier sheet 30.

Temperature of drying the green sheet is preferably 50 to 100° C. anddrying time is preferably 1 to 20 minutes. A thickness of the greensheet after drying is contracted to 5 to 25% of that before drying. Thethickness of the green sheet 10 a after drying is preferably 3 μm orless.

(2) A carrier sheet 20 is prepared separately from the above carriersheet 30, and a release layer 22 is formed thereon. On top thereof, anelectrode layer 12 a having a predetermined pattern is formed. On asurface of the release layer 22 where the electrode layer 12 a is notformed, a blank pattern layer 24 having substantially the same thicknessas that of the electrode layer 12 a is formed.

As the carrier sheets 20 and 30, for example, a PET film, etc. is used,and those coated with silicon, etc. are preferable to improve therelease property. Thicknesses of the carrier sheets 20 and 30 are notparticularly limited and are preferably 5 to 100 μm.

The release layer 22 preferably contains the same dielectric powder asthe dielectric composing the green sheet 10 a. Also, the release layer22 contains a binder, a plasticizer and a release agent other than thedielectric powder. A particle diameter of the dielectric powder may bethe same as that of the dielectric particles included in the green sheetbut it is preferable to be smaller.

In the present embodiment, a thickness of the release layer 22 ispreferably not more than a thickness of the electrode layer 12 a, andmore preferably, it is set to be a thickness of 60% or less, and furtherpreferably 30% or less.

A method of applying the release layer 22 is not particularly limited,but it has to be formed to be extremely thin, so that an applying methodusing, for example, a wire bar coater or a die coater is preferable.Note that adjustment of the release layer 22 thickness can be made byselecting a wire bar coater having a different wire diameter. Namely, tomake the thickness of the release layer 22 to be applied thinner, it canbe done by selecting one having a small wire diameter, inversely, toform it thick, one with a large wire diameter may be selected. Therelease layer 22 is dried after being applied. The drying temperature ispreferably 50 to 100° C. and the drying time is preferably 1 to 10minutes.

A binder for the release layer 22 is composed, for example, of anacrylic resin, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol,polyolefin, polyurethane, polystyrene, or an organic composed of acopolymer of these or emulsion. The binder contained in the releaselayer 22 may be the same as the binder contained in the green sheet 10 aor may be different from that, but preferably the same.

A plasticizer for the release layer 22 is not particularly limited and,for example, phthalate ester, dioctyl phthalate, adipic acid, phosphateester and glycols, etc. may be mentioned. The plasticizer to becontained in the release layer 22 may be the same as that contained inthe green sheet or may be different from that.

A release agent for the release layer 22 is not particularly limitedand, for example, paraffin, wax and silicone oil, etc. may be mentioned.A release agent contained in the release layer 22 may be the same asthat contained in the green sheet or may be different from that.

A binder is contained in the release layer 22 by preferably 2.5 to 200parts by weight, more preferably 5 to 30 parts by weight, andparticularly preferably 8 to 30 parts by weight or so with respect to100 parts by weight of dielectric particle.

A plasticizer is preferably contained in the release layer 22 by 0 to200 parts by weight, preferably 20 to 200 parts by weight, and morepreferably 50 to 100 parts by weight with respect to 100 parts by weightof the binder.

A release agent is preferably contained in the release layer 22 by 0 to100 parts by weight, preferably 2 to 50 parts by weight, and morepreferably 5 to 20 parts by weight with respect to 100 parts by weightof the binder.

After forming the release layer 22 on the surface of the carrier sheet,an electrode layer 12 a to compose an internal electrode layer 12 afterfiring is formed to be a predetermined pattern on the surface of therelease layer 22. A thickness of the electrode layer 12 a is preferably0.1 to 2 μm, and more preferably 0.1 to 1.0 μm or so. The electrodelayer 12 a may be configured by a single layer or two or more layershaving different compositions.

The electrode layer 12 a can be formed on the surface of the releaselayer 22 by a thick film formation method, such as a printing methodusing an electrode coating material, or a thin film method, such asevaporation and sputtering. When forming the electrode layer 12 a on thesurface of the release layer 22 by a screen printing method or a gravureprinting method as a kind of thick film method, it is as follows.

First, an electrode coating material is prepared. The electrode coatingmaterial is fabricated by kneading a conductive material composed of avariety of conductive metals and alloys, or a variety of oxides, organicmetal compounds or resinates, etc. to be conductive materials afterfiring with an organic vehicle.

As a conductive material to be used when producing the electrode coatingmaterial, Ni, a Ni alloy and a mixture of these are used. A shape of theconductive materials is not particularly limited and may be a sphericalshape and scale-like shape, etc. or a mixture of these shapes. Thosehaving an average particle diameter of the conductive material ofnormally 0.1 to 2 μm, and preferably 0.2 to 1 μm or so may be used.

An organic vehicle contains a binder and a solvent. As the binder, forexample, ethyl cellulose, an acrylic resin, polyvinyl butyral, polyvinylacetal, polyvinyl alcohol, polyolefin, polyurethane, polystyrene, or acopolymer of these may be mentioned. Particularly, butyrals, such aspolyvinyl butyral, are preferable.

The binder is contained in the electrode coating material by preferably8 to 20 parts by weight with respect to 100 parts by weight of theconductive material (metal powder). As a solvent, any of well-knownones, such as terpionel, butylcarbitol and kerosene, may be used. Acontent of the solvent is preferably 20 to 55 wt % or so with respect tothe entire coating material.

To improve the adhesiveness, the electrode coating material preferablycontains a plasticizer. As a plasticizer, benzylbutyl phthalate (BBP)and other phthalate esters, adipic acids, phosphoric esters, andglycols, etc. may be mentioned. The plasticizer in the electrode coatingmaterial is preferably 10 to 300 parts by weight, and more preferably 10to 200 parts by weight with respect to 100 parts by weight of thebinder. Note that when an adding quantity of the plasticizer or adhesiveis too large, it is liable that strength of the electrode layer 12 aremarkably declines. Also, to improve transferability of the electrodelayer 12 a, it is preferable to improve adhesiveness and/or adherence ofthe electrode coating material by adding a plasticizer and/or adhesivein the electrode coating material.

After or before forming the electrode coating material layer in apredetermined pattern on the surface of the release layer 22 by aprinting method, a blank pattern layer 24 is formed to be substantiallythe same thickness as that of the electrode layer 12 a on the surface ofthe release layer 22 not formed with the electrode layer 12 a. The blankpattern layer 24 is composed of the same material as that of the greensheet and formed by the same method. The electrode layer 12 a and theblank layer 22 are dried in accordance with need. The drying temperatureis not particularly limited, but is preferably 70 to 120° C., and thedrying time is preferably 5 to 15 minutes.

(3) After that, the electrode layer 12 a is adhered to the surface ofthe green sheet 10 a. For that purpose, the electrode layer 12 a and theblank pattern layer 24 are pressed against the surface of the greensheet 10 a together with the carrier sheet 20, heated and pressed totransfer the electrode layer 12 a and the blank pattern layer 24 to thesurface of the green sheet 10 a. Note that when seeing from the greensheet side, the green sheet 10 a is transferred to the electrode layer12 a and the blank pattern layer 24.

Heating and pressing at the time of transferring may be pressing andheating by a press or by a calendar roll, but is preferably performed bya pair of rolls. The heating temperature and the pressing force are notparticularly limited.

By stacking green sheets formed with a single-layer electrode layer 12 aof a predetermined pattern on the single green sheet 10 a, a stackedblock, wherein a large number of the electrode layers 12 a and the greensheets 10 a are alternately stacked, is obtained. After that, an outerlayer green sheet (a little thicker stacked body obtained by stacking aplurality of green sheets not formed with an electrode layer) is stackedon the lower surface of the stacked body. After that, after forming anouter layer green sheet on the upper side of the stacked body in thesame way, final pressure application is performed.

Pressure at the time of the final pressing is preferably 10 to 200 MPa.Also, the heating temperature is preferably 40 to 100° C. After that,the multilayer body is cut to be a predetermined size to form greenchips. The green chips are subjected to binder removal processing andfiring processing, then, thermal treatment is performed in order tore-oxidize the dielectric layer.

The binder removal processing may be performed under a normal condition,but when using a base metal, such as Ni and a Ni alloy, as a conductivematerial of the internal electrode layer, it is preferably performedunder the specific condition below.

temperature rising rate: 5 to 300° C./hour, particularly 10 to 50°C./hour

holding temperature: 200 to 400° C., particularly 250 to 350° C.

holding time: 0.5 to 20 hours, particularly 1 to 10 hours

atmosphere: a mixed gas of wet N₂ and H₂

A firing condition is preferably as below.

temperature rising rate: 50 to 500° C./hour, particularly 200 to 300°C./hour

holding temperature: 1100 to 1300° C., particularly 1150 to 1250° C.

holding time: 0.5 to 8 hours, particularly 1 to 3 hours

cooling rate: 50 to 500° C./hour, particularly 200 to 300° C./hour

atmosphere gas: a mixed gas of wet N₂ and H₂, etc.

Note that oxygen partial pressure in an atmosphere in the air at firingis preferably 10⁻² Pa or less, particularly 10⁻² to 10⁻⁸ Pa. Whenexceeding the above ranges, the internal electrode layer tends tooxidize, while when the oxygen partial pressure is too low, abnormalsintering is caused in an electrode material of the internal electrodelayer to be broken.

The thermal treatment after performing such firing is preferablyperformed with a holding temperature or highest temperature of 1000° C.or higher, more preferably 1000 to 1100° C. When the holding temperatureor the highest temperature at the time of the thermal treatment is lowerthan the above ranges, it is liable that oxidization of the dielectricmaterial is insufficient to make the insulation resistance lifetimeshort, while when exceeding the above ranges, Ni in the internalelectrode oxidizes and the capacity decreases, moreover, Ni reacts witha dielectric base and the lifetime also tends to become short. Theoxygen partial pressure at the time of thermal treatment is higher thana higher oxygen partial pressure than a reducing atmosphere at the timeof firing, preferably 10⁻³ Pa to 1 Pa, and more preferably 10⁻² Pa to 1Pa. When it is lower than the above range, re-oxidization of thedielectric layer 2 becomes difficult, while when exceeding the aboveranges, the internal electrode layer 3 tends to oxidize. Other conditionof the thermal treatment is preferably as below.

holding time: 0 to 6 hours, particularly 2 to 5 hours

cooling rate: 50 to 500° C./hour, particularly 100 to 300° C./hour

atmosphere gas: wet N₂ gas, etc.

Note that to wet a N₂ gas or a mixed gas, etc., for example, a wetter,etc. may be used. In this case, the water temperature is preferably 0 to75° C. or so. Also, the binder removal processing, firing and thermaltreatment may be performed continuously or separately. When performingcontinuously, the atmosphere is changed without cooling after the binderremoval processing, continuously, the temperature is raised to theholding temperature at firing to perform firing. Next, it is cooled andthe thermal treatment is preferably performed by changing the atmospherewhen the temperature reaches to the holding temperature of the thermaltreatment. On the other hand, when performing them separately, afterraising the temperature to the holding temperature at the binder removalprocessing in an atmosphere of a N₂ gas or a wet N₂ gas, the atmosphereis changed, and the temperature is furthermore raised for firing. Aftercooling the temperature to the holding temperature at the thermaltreatment, it is preferable that the cooling continues by changing theatmosphere again to a N₂ gas or a wet N₂ gas. Also, in the thermaltreatment, after raising the temperature to the holding temperatureunder the N₂ gas atmosphere, the atmosphere may be changed, or theentire process of the thermal processing may be in a wet N₂ gasatmosphere.

The thus obtained sintered body (element body 4) is subjected to endsurface polishing, for example, by barrel polishing and sand-blast,etc., then, a terminal electrode coating material is burnt to formterminal electrodes 6 and 8. For example, a firing condition of theterminal electrode coating material is preferably in a mixed gas of wetN₂ and H₂ at 600 to 800° C. for 10 minutes to 1 hour or so. Inaccordance with need, soldering, etc. is performed on the terminalelectrodes 6 and 8 to form a pad layer. Note that the terminal electrodecoating material may be fabricated in the same way as the electrodecoating material explained above.

A multilayer ceramic capacitor of the present invention produced asabove is mounted on a print substrate, etc. by soldering, etc. and usedfor a variety of electronic equipments.

In a method of producing a multilayer ceramic capacitor using thedielectric coating material (green sheet coating material) and the greensheet according to the present embodiment, by combining a binder resinincluding a butyral based resin as the main component and an adhesiveagent composed of a xylene based resin, it becomes possible to produce agreen sheet having enough strength to be peeled from a supporting body,preferable adhesiveness and handlability even in the case of anextremely thin green sheet. For example, a thickness of the dielectriclayer after firing (a green sheet after firing) can be made as thin as 5μm or less, preferably 3 μm or less, and more preferably 2 μm or less.Also, the green sheet of the present embodiment is capable of increasingthe number of layers to be stacked because the surface roughness issmall.

Also, in a production method of a multilayer ceramic capacitor using thedielectric coating material (green sheet coating material) and the greensheet according to the present embodiment, a specific kind of dispersanthaving a specific range of HLB is used. Therefore, even an extremelythin green sheet of, for example, 5 μm or thinner is strong enough to bepeeled from the carrier sheet and has preferable adhesiveness andhandlability. Also, surface roughness of the sheet is small andstackability is excellent. Therefore, it becomes easy to stack a largenumber of green sheets via electrode layers.

Furthermore, in a production method of a multilayer ceramic capacitorusing the dielectric coating material (green sheet coating material) andthe green sheet according to the present embodiment, an antistatic agentis contained in the dielectric coating material, and the antistaticagent is an imidazoline based antistatic agent. Therefore, even in thecase of an extremely thin green sheet of, for example, 5 μm or thinner,it is possible to produce a green sheet having sufficient strength to bepeeled from the carrier sheet, wherein electrostatic generated at thetime of being peeled from the carrier sheet is suppressed, and theadhesiveness and handlability are preferable. Also, surface roughness ofthe sheet is small and stackability is excellent. Therefore, it becomeseasy to stack a large number of green sheets via electrode layers.

Also, in a production method of a multilayer ceramic capacitor accordingto the present embodiment, a dry type electrode layer can be easily andhighly accurately transferred to the surface of the green sheet withoutdamaging or deforming the green sheet.

Note that the present invention is not limited to the above embodimentsand may be variously modified within the scope of the present invention.

For example, a method of the present invention is not limited to theproduction method of multilayer ceramic capacitors and may be applied asa production method of other multilayer type electronic devices.

Below, the present invention will be explained based on further detailedexamples, but the present invention is not limited to the examples.

EXAMPLE 1a Production of Green Sheet Coating Material

As a starting material of ceramic powder, BaTiO₃ powder (BT-02 made bySakai Chemical Industry Co., Ltd.) was used. A ceramic powdersubcomponent additives were prepared to satisfy (Ba_(0.6)Ca_(0.4))SiO₃:1.48 parts by weight, Y₂O₃: 1.01 parts by weight, MgCO₃: 0.72 wt %,Cr₂O₃: 0.13 wt % and V₂O₅: 0.045 wt % with respect to 100 parts byweight of the BaTiO₃ powder.

First, only the subcomponents were mixed by a ball-mill to obtainslurry. Namely, the subcomponent additives (total amount 8.8 g),ethanol: 6 g, n-propanol: 6 g and xylene: 2 g were preliminary ground bya ball-mill for 20 hours.

Next, the preliminary ground slurry of the subcomponent additives,ethanol: 65 g, n-propanol: 65 g, xylene: 35 g, mineral spirit: 15 g, DOP(dioctyl phthalate) as a plasticizer component: 6 g, a polyethyleneglycol based nonionic dispersant (HLB=5 to 6) as a dispersant: 1.4 g andxylene based resin:1.0 g were added to BaTiO₃: 191.2 g and mixed by aball-mill for 4 hours. Note that as the xylene based resin, additioncondensation resin (not modified) of methaxylene and formalin was used.An average molecular weight of the resin is 200 to 620. An addingquantity of the xylene based resin to the ceramic powder was 0.5 wt %.

Next, the dispersion coating material was added with 15% lacquer (BH6made by Sekisui Chemical Co., Ltd. was dissolved inethanol/n-propanol=1:1) of BH6 (polybutyral resin: PVB) by 6 wt % as asolid content (80 g as a lacquer adding quantity). After that, byball-milling the dispersion coating material for 16 hours, a ceramiccoating material (green sheet coating material) was obtained.

A polymerization degree of a polybutyral resin as the binder resin was1400, a butyralation degree thereof was 69%±3%, and a residual acetylgroup amount thereof was 3±2%. The binder resin was contained by 6 partsby weight in the ceramic coating material with respect to 100 parts byweight of ceramic powder (including ceramic powder subcomponentadditives). Also, when assuming that total volume of the ceramic powder,binder resin and plasticizer in the ceramic coating material was 100volume %, the volume ratio accounted by the ceramics powder was 67.31volume %.

Also, DOP as a plasticizer was contained in the ceramic coating materialby 50 parts by weight with respect to 100 parts by weight of the binderresin. Water was contained by 2 parts by weight with respect to 100parts by weight of the ceramic powder. The polyethylene glycol basednonionic dispersant as a dispersant was contained by 0.7 part by weightwith respect to 100 parts by weight of the ceramic powder.

Also, in the coating material, mineral spirit of at least any one of ahydrocarbon based solvent, industrial gasoline, kerosene and solventnaphtha was added by 5 parts by weight with respect to 100 parts byweight of the ceramic powder. Furthermore, the coating material containsan alcohol based solvent and an aromatic solvent as a solvent. Whenassuming that total weight of the alcohol based solvent and aromaticsolvent was 100 parts by weight, xylene as an aromatic solvent wascontained by 15 parts by weight.

Viscosity of the coating material was 180 mPa·s. The viscosity of thecoating material was measured by using a B-type viscosimeter and usingS21 as a rotor, and measurement was made at a temperature of 25°immediately after the coating material was obtained. The rotation rateat the time of measurement was 50 rpm.

Production of Green Sheet

The coating material obtained as above was applied to a PET film as asupporting film by the doctor blade and dried to produce a green sheethaving a thickness of 12 μm.

Evaluation of Green Sheet

After that, evaluation was made on surface roughness, sheet tensilestrength, adhesiveness (stackability, release strength) and a totalevaluation of the green sheet. The results are shown in Table 1.

Note that the surface roughness was obtained by measuring averagesurface roughness Rz by using a surface roughness measuring device madeby Kosaka Laboratory Ltd. The sheet tensile strength was obtained byusing a tensile test machine of Instron 5543, preparing 5 sheets cut tobe a dumbbell shape as samples, pulling the samples respectively at atensile rate of 8 mm/min., obtaining strength and stretch at the time ofbreaking and calculating an average value.

The adhesiveness was evaluated as below. First, 10 samples obtained bycutting a dried sheet to 50 mm×15 mm were prepared, and 5 sets obtainedby adhering two of the samples each were prepared. Each of the sheetsets was adhered under a condition of 70° C. for one minute under about4 MPa. After that, surfaces of the sheets of each set were appliedtwo-sided tape, the sheets of each set were pulled in the direction ofdetaching by using the tensile test machine of Instron 5543, and releasestrength at the time of being detached was measured. The higher therelease strength, the more excellent it is in adhesiveness.

In the total evaluation, those having surface roughness of 0.3 μm orless, sheet tensile strength of 6.5 MPa or more, and release strength ofadhesiveness of 20 N/cm² or more were determined to be good (o), andthose not satisfying even one of the conditions were determined to bedefective (x). Note that “*” in front of a number in the table indicatesthat it exceeds a preferable range. It is the same also in Tables below.

EXAMPLE 1b

Other than using a polyol-modified xylene based resin (an averagemolecular weight: 700-1000) obtained by modifying the additioncondensation resin of methaxylene and formalin by polyol as a xylenebased resin, a green sheet was produced in the same way as in theexample 1a, and the same evaluation was made. The results are shown inTable 1.

COMPARATIVE EXAMPLE 1a

Other than not adding the xylene based resin, a green sheet was producedin the same way as in the example 1a, and the same evaluation was made.The results are shown in Table 1.

COMPARATIVE EXAMPLES 1b TO 1h

Other than using the tackifier shown in Table 1 instead of a xylenebased resin, a green sheet was produced in the same way as in theexample 1a, and the same evaluation was made. The results are shown inTable 1.

TABLE 1 Adding Quantity Surface Roughness Tensile Strength AdhesivenessTackifier Kind (PHP) (μm) (MPa) (N/cm²) Evaluation Example 1a XylenBased Resin “a” 0.5  0.26 7.10  21.3 ∘ Example 1b Xylen Based Resin “b”0.5  0.27 6.82  21.3 ∘ Comparative Not Added 0 *0.31 7.31  20.6 xExample 1a Comparative Petroleum Resin “a” 0.5 *0.35 7.73 *16.3 xExample 1b Comparative Petroleum Resin “b” 0.5 *0.33 7.95 *10.8 xExample 1c Comparative Rosin Based Resin “a” 0.5 *0.35 7.78 *14.1 xExample 1d Comparative Rosin Based Resin “b” 0.5 *0.31 7.67 *10.1 xExample 1e Comparative Terpene Based Resin “a” 0.5  0.29 6.86 *10.5 xExample 1e Comparative Terpene Based Resin “b” 0.5  0.27 *5.92  *12.3 xExample 1f Comparative Acrylic Resin “a” 0.5 *0.38 *5.92  *16.9 xExample 1g Comparative Acrylic Resin “b” 0.5 *1.03 *4.63  *10.2 xExample 1h

Evaluation 1

As shown in Table 1, it was confirmed that the green sheets according tothe examples exhibited improved surface roughness and adhesivenesscomparing with the case of not adding a xylene based resin. Also, in thecases of other tackifier, it was confirmed that the adhesiveness and/ortensile strength declined and surface roughness deteriorated comparingwith the case of not adding.

EXAMPLES 2a TO 2d

As shown in Table 2 below, other than changing an adding quantity of axylene based resin in a range of 0.1 to 1.5 wt % (PHP) with respect tothe ceramic powder, a green sheet was produced in the same way as in theexample 1a, and the same evaluation was made. The results are shown inTable 2.

TABLE 2 Adding Quantity Surface Roughness Tensile Strength AdhesivenessTackifier Kind (PHP) (μm) (MPa) (N/cm²) Evaluation Comparative Not Added0.0 *0.31 7.31 20.6 x Example 1a Example 2a Xylen Based Resin a 0.1 0.37.28 20.6 ∘ Example 2b Xylen Based Resin a 0.5  0.26 7.10 21.3 ∘ Same asExample 1a Example 2c Xylen Based Resin a 1.0  0.28 6.82 22.0 ∘ Example2d Xylen Based Resin a 1.5 *0.35 6.53 23.1 x

Evaluation 2

It was confirmed that it is preferable to add a xylene based resin in arange of 1.0 wt % or less, more preferably 0.1 or more and 1.0 wt % orless, and particularly preferably more than 0.1 and 1.0 wt % or less.Also, it was confirmed that, when the adding quantity of the xylenebased resin was too small, adhesiveness tended to decline, while whenthe adding amount was too large, the adhesiveness improves but it wasliable that surface roughness increases, stacking of layers by a largenumber became difficult, tensile strength of the sheet declined, andhandlability of the sheet declined.

COMPARATIVE EXAMPLES 3a AND 3b

Other than using a polyvinyl acetal resin (PVAc) of a production numberBX-1 made by Sekisui Chemical Co., Ltd. and an acrylic resin (MMA-BA)having a molecular weight of 450000 and a Tg of 70° C. instead of PVB asa binder resin as shown in Table 3, a green sheet was produced in thesame way as in the example 1, and the same evaluation was made. Theresults are shown in Table 3.

TABLE 3 Resin Adding Quantity Surface Roughness Tensile StrengthAdhesiveness Binder Resin Kind (PHP) (μm) (MPa) (N/cm²) EvaluationExample 1a PVB 6  0.26  7.10 21.3 ∘ Comparative PVAc 6 *0.62  6.6 *3.2 xExample 3a Comparative Acryl(MMA-BA) 6 *0.51 *1.2 *6.6 x Example 3b

Evaluation 3

As shown in Table 3, it was confirmed that a polyvinyl butyral resin(PVB) was preferable as a binder resin. Namely, a combination of PVB asa binder resin and a xylene based resin as a tackifier was confirmed tobe preferable in terms of improving surface roughness, tensile strengthand adhesiveness of the green sheet.

As explained above, according to the present invention, it is possibleto provide a green sheet coating material, a green sheet, a productionmethod of a green sheet coating material and a production method of agreen sheet capable of producing a green sheet having enough strength tobe peeled from a supporting body, preferable adhesiveness andhandlability even in the case of an extremely thin green sheet.Therefore, it is possible to provide a production method of anelectronic device suitable to making the electronic device thin andmultilayer.

1. A green sheet coating material, comprising ceramic powder and abinder resin containing a butyral based resin as the main component; andfurthermore comprising a xylene based resin as a tackifier.
 2. The greensheet coating material as set forth in claim 1, wherein said xylenebased resin is contained in a range of 1.0 wt % or less with respect to100 parts by weight of said ceramic powder.
 3. The green sheet coatingmaterial as set forth in claim 1, wherein said butyral based resin is apolybutyral resin; and a polymerization degree of said polybutyral resinis 1000 or higher and 1700 or lower, a butyralation degree of the resinis higher than 64% and lower than 78%, and a residual acetyl groupamount is less than 6%.
 4. The green sheet coating material as set forthin claim 1, wherein said binder resin is contained by 5 parts by weightor more and 6.5 parts by weight or less with respect to 100 parts byweight of said ceramic powder.
 5. The green sheet coating material asset forth in claim 1, containing dioctyl phthalate as a plasticizer by40 parts by weight or more and 70 parts by weight or less with respectto 100 parts by weight of said binder resin.
 6. A production method of aceramic green sheet, comprising the steps of: preparing a green sheetcoating material as set forth in claim 1; and forming a ceramic greensheet by using said green sheet coating material.
 7. A production methodof a ceramic electronic device, comprising the steps of: preparing agreen sheet coating material as set forth in claim 1; forming a ceramicgreen sheet by using said green sheet coating material; drying saidgreen sheet; stacking dried green sheets via internal electrode layersto obtain a green chip; and firing said green chip.
 8. A green sheetproduced by using a green sheet coating material as set forth inclaim
 1. 9. The green sheet coating material as set forth in claim 1,wherein said xylene based resin is an addition condensation resin ofmethaxylene and formalin, or those obtained by modifying the additioncondensation resin.